Model Answer
0 min readIntroduction
Lichen planus (LP) is a chronic inflammatory condition affecting the skin, mucous membranes, hair, and nails. It is an immune-mediated disease, believed to be triggered by an autoimmune response to antigens in the basal keratinocytes. The classic presentation involves pruritic, purplish, polygonal, planar papules, but the disease exhibits significant clinical heterogeneity. Understanding the varied manifestations and correlating them with the underlying histopathology is essential for accurate diagnosis and management. This answer will detail the cutaneous, mucosal, follicular, and nail presentations of lichen planus, followed by a comprehensive description of its histopathological features and their clinical relevance.
Cutaneous Manifestations
The skin is the most commonly affected site in lichen planus. The typical lesions are:
- Papules: Small, flat-topped, polygonal, violaceous papules, usually 2-10mm in diameter.
- Pruritus: Intense itching is a hallmark symptom.
- Distribution: Commonly affects flexural areas (wrists, ankles), but can be widespread.
- Koebner Phenomenon: New lesions develop at sites of skin trauma.
- Hyperpigmentation: Post-inflammatory hyperpigmentation is common after lesion resolution.
- Lichen planus annularis: Presents as expanding, ring-shaped lesions.
- Lichen planus vesiculosus: Characterized by blister formation.
Mucosal Manifestations
Mucosal involvement occurs in up to 70% of patients with lichen planus. The oral mucosa is most frequently affected.
- Oral Lichen Planus: Presents as white, lacy (Wickham's striae) or erosive lesions on the buccal mucosa, tongue, and gingiva.
- Genital Lichen Planus: Can cause pain, dyspareunia, and urethral strictures.
- Esophageal Lichen Planus: Rare, but can cause dysphagia.
Follicular Manifestations
Lichen planopilaris is a scarring alopecia characterized by inflammation around hair follicles.
- Inflammatory Papules: Red, scaly papules surrounding hair follicles.
- Scarring Alopecia: Permanent hair loss in affected areas, often leading to patches of baldness.
- Perifollicular Erythema: Redness around the hair follicles.
Nail Manifestations
Nail involvement occurs in approximately 10-20% of patients.
- Longitudinal Ridging: Vertical lines on the nail plate.
- Splinter Hemorrhages: Small, linear blood spots under the nail.
- Nail Dystrophy: Thickening, thinning, or splitting of the nail.
- Pterygium Unguis: Cuticle adheres to the nail plate.
- Subungual Hypertrophy: Thickening of the nail bed.
Histopathological Features
The histopathological features of lichen planus are relatively characteristic, although variations can occur depending on the stage of the lesion and the site of involvement.
- Epidermis: Hyperkeratosis, irregular acanthosis (thickening of the spinous layer), and basal cell degeneration.
- Dermo-Epidermal Junction: A characteristic "saw-tooth" appearance due to irregular downward projections of the epidermis.
- Infiltrate: A dense, band-like infiltrate of lymphocytes primarily in the superficial dermis, immediately beneath the epidermis. This is a key diagnostic feature.
- Colloid Bodies: Degenerated basal keratinocytes surrounded by a hyaline material, representing Civatte bodies.
- Melanin Incontinence: Melanin pigment within the dermal macrophages.
- Interface Dermatitis: Inflammation at the junction between the epidermis and dermis.
Relevance to Clinical Presentation
The histopathological features directly correlate with the clinical manifestations:
- Band-like infiltrate: Explains the inflammatory papules and pruritus.
- Basal cell degeneration & Colloid bodies: Contribute to the purplish color and scaling of the lesions.
- Saw-tooth pattern: Reflects the irregular epidermal thickening and contributes to the planar appearance of the papules.
- In mucosal LP, the infiltrate is often band-like but may be less dense and more chronic.
- In lichen planopilaris, the infiltrate surrounds the hair follicles, leading to scarring and alopecia.
It's important to note that histopathology is not always definitive, and correlation with clinical findings is crucial for accurate diagnosis.
Conclusion
Lichen planus is a multifaceted inflammatory condition with diverse clinical presentations affecting the skin, mucosae, follicles, and nails. The characteristic histopathological features, including the band-like infiltrate, colloid bodies, and saw-tooth pattern, provide valuable diagnostic clues and correlate with the observed clinical symptoms. A thorough understanding of both the clinical and histological aspects of lichen planus is essential for effective diagnosis and management, ultimately improving patient outcomes. Further research into the immunopathogenesis of LP is needed to develop more targeted therapies.
Answer Length
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